1st thing I would do is check the voltage with the key on engine off and with the throttle closed. Here's a good video. https://lmr.com/products/Mustang-Throttle-Position-Sensor-TPS-Install-Adjust

Check your timing is set correctly before doing anything.  

TremendousWand wrote:

Check your timing is set correctly before doing anything.  

Remember that to set base timing you need to unplug the inline spout connector.  Then set the timing to spec. on a warm engine. 

On TPS voltage, if its adjustable you want to shoot for just under 1 volt.  I used to go for like 0.97-0.98.  But, I've also done a lot of reading that says this may be total BS, and so long as the value is between like 0.5-1.5 the ECU just figures throttle position based on the voltage at lowest and highest readings, in essence its actually seeing where the throttle is when closed and at maximum opening.  Some of this may be strategy based as well, so if you have the ability to adjust it I would still do it. 

Michael H. wrote:

I've been sick, so I haven't been able to look at it yet, but everything I have read says that the 4.9L TPS is not adjustable...though I'm tempted to slot the holes so I can make it adjustable.

It can't hurt to check the timing but I feel like it's ok because it hasn't been touched... The only change I made was to change the TPS.  It actually drove and performed fine with the old TPS, but I had a check engine light on.

As far as idle, it's fine (i.e. no surging)... it just takes 30 seconds or so to come back down to idle so there's not enough time to drop back to idle between shifts.

It's also worth noting that it doesn't do this all of the time, but it does it probably 90% of the time.

Keep in mind simply loosening the TPS bolts will allow you to move the sensor. Slotted or not. If you need more you can slot it, but usually you can just move it then re-tighten.
 

Last edited by Raymond_B (11/02/2017 1:12 PM)

FWIW, just because you are getting a CEL with a code corresponding to a particular part doesn't mean that part's bad.  The diagnostics in no EFI system are that good.  The code is telling you that the ECU "perceives" the TPS voltage to be out of range.  What its not telling you is when.  Its entirely possible that your issue is not actually related to the TPS, but rather another sensor, or even a mechanical problem.  Based on symptoms I would give the IAC a serious look.  That code could be the result of the IAC being too far closed for a particular TPS voltage, which would explain the high idle. 

I've had an O2 code before that was actually caused by a faulty MAF, and other similar issues.  The ECU is a good design, and the diagnostics can be helpful, but just like pre EFI cars the diagnostics are not a substitute for sound mechanical and electrical troubleshooting.  The codes you get are in effect the ECU's best guess as to what's causing your issue.  Smart as it is its constrained by the feedback systems it uses and its programming.  Its not really some omniscient device that actually knows what's happening in the engine at any given time.  Sometimes you have to be smarter than it in order to solve an issue. 

So it seems that now the ECU considers that TPS to be in the correct range voltage wise for the other conditions its "seeing".  I have to surmise that either the throttle blade is getting hung up or the TPS voltage is off.  I'm also wondering if the TPS could be causing the hangup.  Where'd you source the TPS from? 

TKOPerformance wrote:

So it seems that now the ECU considers that TPS to be in the correct range voltage wise for the other conditions its "seeing".  I have to surmise that either the throttle blade is getting hung up or the TPS voltage is off.  I'm also wondering if the TPS could be causing the hangup.  Where'd you source the TPS from? 

The TPS came from Autozone... maybe that's part of the problem.

 

Michael H. wrote:

50vert wrote:

Just to be sure that adaptive learning is not affecting the data, (not even sure that speed density uses it), did you reset the ecu after replacing the tps?

Yes. I unhooked the battery and left it unhooked for 20 minutes or so.
It's only supposed to take about 15 minutes to reset, right?
 

They have a capacitor that needs to bleed down for the EEC to lose it's adaptive memory. I've had various luck from 1-2 hours to having to leave it over night (my 95 Lightning would take forever) it was also SD by the way.

Have you made the adjustment yet?
 

Last edited by Raymond_B (11/07/2017 2:32 PM)

I finally got around to checking the TPS voltage.  It is reading .79, which is in the acceptable range according to the video you shared above.